Reciprocating engines are frequently tested in order to determine the condition of their cylinders. Leakage or flow rating is one technique used for such testing while compression testing is a further technique. If the cylinder being tested meets specifications for such testing, the cylinder is assumed to be in good condition. If the cylinder does not meet specifications, it is assumed that replacement of the piston rings, valves, piston or cylinder is necessary.
In testing using flow rating techniques, the cylinder is tested under both "dry" and "wet" conditions. That is, the cylinder is initially tested by applying a pressure to the cylinder and determining the flow rate of air which is required to hold this pressure. Subsequently, the cylinder walls are "wetted" with oil and the test is again conducted. Such testing can also involve detection of leakage at either the exhaust or intake valves or at the air start valves by ultrasonic techniques. If the leakage is reduced under "wet" conditions, the individual conducting the cylinder diagnosis can be reasonably confide that it is the rings that are defective. If no reduction occurs under wet conditions, then it is reasonably concluded that the valves are at fault.
The wet test described involves the insertion of an oil nozzle into the cylinder through the spark plug hole and emitting oil from the nozzle in order to attempt to form a seal between the piston rings and the cylinder wall with the oil. Following the insertion of the oil, the leakage test is again performed to determine the quantity of air required to maintain the predetermined pressure. If the quantity of air required is substantially less than initially required, it may reasonably be assumed the piston rings are defective in that cylinder.
There are, however, problems with existing "wet" techniques. The oil nozzle used emits oil only directly outwardly from the nozzle and coaxial with it. This may result in an uneven coating of oil on the cylinder walls. In using such a nozzle assembly, therefore, there is an added uncertainty in the results of the subsequent leakage tests and, therefore, the results may not give an accurate portrayal of actual cylinder conditions.